Hydraulic drive and actuator

ABSTRACT

An actuator having two heads and a pipe as cylinder chamber, releasably mounted between the heads. The pipe is selected from a plurality of differently wide and/or differently long pipes to provide different dimensions for the cylinder chamber. The heads are provided to accommodate the differently wide pipes and a matching piston is removably mounted on the piston rod.

United States Patent [191 Paul et a1.

[ 51 Feb. 20, 1973 v HYDRAULIC DRIVE AND ACTUATOR Inventors: Werner Paul, 2874 Lemwerder; Dlerk Schumann, 2800 Bremen, both of Germany Vereinigte Flugtechnische Werke- Fokker GmbH, Bremen, Germany Filed: April 15, 1971 Appl. No.: 134,133

Assignee:

0.8. CI ..92/128, 92/169 Int. Cl. ..F01b 29/08, FOlb 31/00 Field of Search ..92/l28, 171, 164, 169, 170, 92/59 References Cited UNITED STATES PATENTS 7/1930 Stanley ..92I59 2,953,118 Flick et a1 ..92/1 64 2,480,633 8/1949. Christensen. ....92/1 64 3,334,773 8/1967 Bimba ....92/l28 X 3,420,148 1/1969 Doerfer et a1. ..92/1 64 X Primary ExaminerMartin P. Schwadron Assistant Examiner-Allen M. Ostrager Attorney-Smyth, Roston & Pavitt [57 ABSTRACT 7 Claims, 2 Drawing Figures ill,

HYDRAULIC DRIVE AND ACTUATOR The present invention relates to a hydraulic actuator or linear motor which includes a cylinder with two heads and with a cylindric pipe as piston chamber for receiving an operating piston.

Hydraulic motors of this type are frequent'y used to obtain particular, controlled actuation displacement under power for purposes of control and positioning operations, and they are used particularly to provide linear displacement for purposes of controlling mechanical motion, position, force or accelerations. I-Iydraulically controlled actuators of this type provide for such controlled displacement at a high degree of accuracy, and they exhibit considerable dynamic efficiency and capabilities. Of course, the conditions under which hydraulic actuators operate differ greatly, particularly in case a hydraulic actuator is to be used in experimental circuits. Here, then, arises the requirement of adapting the particular hydraulic actuator to the operating conditions, but it is often precisely the purpose of these experiments to find particulars of these conditions. Studies along that line are made particularly in case of regulator and feedback systems using hydraulic components as actuator and power amplifier output stage. These systems require the operating piston surface area (force) and the effective cylinder chamber volume (piston displacement) to be adapted to the desired and required power range (often yet to be found). Such accurate adaptation is necessary as oversized actuators have reduced performance as to dynamic characteristics, and accuracy deteriorates, while undersizing may cause operational breakdown.

The known hydraulic actuators and linear servo motors are often constructed in that a tubular piston chamber with an operating piston is disposed between two cylinder heads. These types of actuators and servo motors are adapted and proportioned to the particular operating conditions through selection of a suitable piston surface and selection of a particular displacement range for the piston stroke. The selection amounts to the generation of a particular operating characteristic. This means that for a different operating characteristic, these particular parameters have to be changed. However, stroke length and piston dimensions cannot just be adjusted, but the particular construction of the actuator has to be altered which amounts to a complete replacement of the unit. This, of course, is a costly disadvantage particularly in cases where a considerable number of different actuators have to be used and each is to operate under somewhat different conditions. Moreover, in case of experiments and design development, reconstruction is too time consuming, so that differently dimensioned actuators have to be available for matching. The requirement of making various types of hydraulic motors available when only one is expected to be used finally, is quite expensive.

It is an object of the present invention to suggest construction for an actuator which permits ready adaptation to different operating conditions and ready selection of a particular operating characteristic. In accordance with the present invention, it is suggested that the cylinder heads are provided with receiving and sealing systems so as to receive cylinder pipes of various inner diameter and independently from length, so that required adaptation is reduced to an exchange and selection of a suitably long. and wide pipe as cylinder chambers.

While the specification'concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 illustrates cross section through an actuator constructed in accordance with the preferred embodiment of the present invention; and

FIG. 2 illustrates a partial cross section through the actuator with an exchanged piston and piston chamber.

Proceeding to the detailed description of the drawings, there is illustrated an actuator provided and constructed for ready adaptation to different operating conditions, i.e. provided for selection and modification of suitable operating characteristics.

The basic components of the actuator are two cylinder heads 1 and 20 with attachments to be described. Selected, different pipes are disposed between them. Pipe 7 in FIG. 1 is one of them, pipe 27 in FIG. 2 is a different one. The pipes, as disposed between the heads, define the cylinder chamber proper and define particularly width (diameter) and length.

(axially) of the piston chamber.

Turning to the first cylinder head 1, it is provided at its outside end (axially) with a protective pipe 2 for receiving one end of a piston rod 11. Pipe 2 has a flange and is bolted therewith to head 1. A threaded bolt 3 is threaded into pipe 2, and the bolt itself is provided with an eye 4. A lock nut 5 secures the bolt in its threaded position. Bolt 3 with eye 4 is provided for positioning, mounting and installing the actuator as to stationary reference and support.

On the other side, i.e. axially opposite to pipe 2, head 1 is provided with a plural stage, blind end bore 6 in representation of plural, coaxial blind end bores of staggeredly reduced diameters. Specifically, the bore has two stages defined by short cylindrical bores 61 and 63 of differing diameter, but having coaxial relation. The blind end of bore 61 is defined by an axial annulus 62 serving as axial abutment surface, while annulus 64 is the end face proper of the blind bore 6. Bore 61 is the larger diameter or upper stage portion and bore 63 is the smaller diameter or lower stage portion of the blind bore. Each stage can also individually be termed a blind bore, the plurality of bores being arranged coaxially with staggered diameter reduction.

The two-stage blind bore 6 is provided for receiving cylindrical pipes of differing outer (and inner!) diameter, whereby each pipe (such as 7 and others) are provided with an indexing end that fits into one of the stages. In the particular example, cylinder defining pipe 7 is provided with an axial shoulder 72 that is placed in abutment with shoulder annulus 62, while a fitting and indexing portion 71 of pipe 7 is inserted, snuggly received by and placed in sealing engagement with the larger diameter portion 61 of bore 6.

In order to seal the respective cylinder chamber pipe, generally, the several stages are provided with coaxial grooves, such as 8 and 9, for receiving washers or sealing rings, such as 91 in groove 9. This packing may be provided only where needed so that ring-shaped groove 8 in the lower stage 63 of bore 6 is shown as being empty.

The head 1 is provided, in addition, with a passage or bore 10 disposed coaxial to bore 6. The piston rod 11 traverses and is received by bore 10. Protective pipe 2 serves as coaxial cover, to close bore 10 from the other side but to receive the piston rod upon displacement to the left. In the interior of pipe 7, i.e., within the cylinder chamber proper, an operating piston 12 is removably mounted on piston rod 11 by means of clamping elements 13. The piston 12 is a ring of outer diameter fitting into pipe 7, and is provided with suitable packing.

The second head of the system 20 has a central bore 25, traversed by portions of piston rod 11, closer to the other end thereof. An eye 41 is secured to the other, outwardly projecting end of piston rod 11. The eye 41 is provided for connection to an object that is to be displaced by operation of the particular hydraulic motor.

Head 20 is provided with a two-stage blind bore, having a larger diameter stage 21, and a smaller diameter stage 23, and axial annuli 22 and 24. Pipe 7 has a shoulder 73 close to the end as inserted in head 20 and in abutment with annulus or shoulder 22, while a fitting pipe end portion 74 is snuggly received by bore 21. Bores 21, 23 and 25 are,of course, coaxial. The two coaxial blind bores 21 and 23 are also provided with ring-shaped grooves 28 and 29, so as to receive sealing rings in the illustrated example, a washer ring 49 is disposed in groove 29 of the larger diameter bore 21.

The two cylinder heads 1 and 20, after having 1 received a particularly selected, cylinder-chamberdefining pipe, such as 7, are bolted together by means of suitable clamping equipment, such as tie rods 30, threaded or otherwise bolted to cylinder heads 1 and 20, i.e. in the annular front walls In and 20a, respectively, facing each other. Upon tightening tie rods 30, pipe 7 is positively positioned between the two heads; particularly, shoulders 71 and 73 of pipe 7 are urged into abutment with annuli 62 and 22. A tubular conduit 31 connects a governor 35 on head 1 with a connecting pipe 36 on head 20. A second tubular conduit 32 extends between a regulator valve 37 on head 1 and a connecting pipe 38 on head 20. A duct or passageway 39 leads from connecting pipe 38 to the interior of the cylinder chamber. There is a similar duct from pipe end 36 through head 20 and leading also to the cylinder chamber at the other end of pipe 7. Analogously, the regulator valve 37 is in communication with the cylinder chamber via a duct 40 in head 1, and there is a similar duct between the cylinder chamber and the governor 35 in the same head. All these elements on heads 1 and 20 can be similar for wide ranges of piston forces and strokes.

Turning now to FIG. 2, there is illustrated part of the actuator, showing the same head 1, but having a different pipe 27 inserted. There is, in particular, a smaller diameter end portion 26 that fits into bore 61', a washer 48 being inserted in groove 8. The pipe 27 abuts annulus 64 directly within axial end face. Pipe 27 defines a smaller diameter piston chamber, and correspondingly, there is a smaller piston 42 clamped onto piston rod 11 by means of suitable fasteners 43.

- As can readily be seen from the illustrate'd'embodiment, the actuator can be adapted readily to different conditions. Its operating characteristics can be selected through selection of a suitably dimensioned cylinder chamber defining pipe and of a correspondingly dimensioned, matching piston to be placed on the piston rod. Length as well as diameter of the cylinder chamber are selectable in that manner, so that piston force and displacement volume of the actuator, one or both of these parameters, are subject to such selection and adjustment.

The plural stages of the pipe receiving bores in heads 1 and 20 can be regarded as coarse adjustment parameter. The inner diameters of the pipes can be selected on a more finely graded scale; different pipes may have fitting sections dimensional similar to the particular indexing sections 72 and 74 of pipe 7. In other words, pipes of different internal diameter may well have similar indexing sections for fitting into the same blind bore stages 61 and 21 (or 63 and 23). Of course, length selections may cover a range in any gradation. Thus, a suitable set of pipes will include subsets of differently long pipes for the same inner diameter. Restrictions in the available variations of piston stroke are the axial length of the tubular interior of cover pipe 2 as not occupied by bolt 3, plus the length of bore 10. But also here, cover pipe 2 may be exchangeable for a longer one. Also, the diameter of v the largest bore stage limits available diameter range for the piston chamber. However, a two-stage blind bore in each head is just one (though preferred) example of practicing the invention; more stages could be provided.

It can, therefore, readily be seen that the same heads can be used for various piston chamber dimensions. Also, the same piston rod may be used. Adaptation and selection therefore involves merely selection of a suitable combination of pipe and piston. Additionally, suitable tie rods have to be provided for differently long chambers, but the tie rods may well be sectionalized, having removable inserts for matching the desired piston chamber length. Also, conduits 31 and 32 may have to be exchanged, but flexible tubing could be used to accommodate different distances between the heads 1 and 20. Using the same piston rod (and changing only pistons thereon) has the added advantage, that minimum piston rod projection from head 20 is constant parameter (the other end of the rod being in pipe 2 to the full length of the tubular interior thereof).

The principal advantage of the invention becomes evident when practiced in those cases where a hydraulic actuator, linear motor etc. is to be used for a particular task and where the operating conditions per se are known only fairly accurate (e.g. by order of magnitude). The dimensions and the piston can, therefore, be changed on location, e.g., after having experimentally determined the response of the object to be driven by the piston rod. The expensive parts of the hydraulic system, e.g., the heads 1 and 20 and the regulator parts on them, remain the same, only the relatively inexpensive parts which, in fact, can be regarded as staple articles, such as pistons, pipes, rods, etc., may be readily provided in large quantities for suitable selection.

The piston rod 11 may at times require also a change, particularly if a very large displacement or a very small displacement is desired, so that the standard piston rod may be accordingly too small or too large. This again may be important in case the servo motor is part of a feedback control system wherein all movable masses, including the piston rod, may be required to be adapted and to be matched very accurately to the dynamic conditions of the loop.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

We claim:

1. Hydraulic actuator comprising 'a first cylinder head, a second cylinder head, each provided with plural coaxial, axially staggered blind bores of different diameter and an axial ring face between respective two bores, for receiving pipes of different outer diameter, and for sealingly engaging and positioning such a pipe;

a selected pipe having two ends and removably disposed with its two ends in one blind bore each respectively of the first and second heads, a cylindrical wall as defining each bore provided with a groove for receiving a washer, the axial ring face for axial engagement with the respective pipe;

means for tightening the two heads towards each other to positively position the pipe between the two heads; and

a piston rod with piston disposed in the pipe.

2. Actuator as in claim 1, the piston removably clamped onto the piston rod.

3. Actuator as in claim 1, the pipe having an axial shoulder near its ends to engage the ring faces of the head.

4. Actuator as in claim 1, each head including a passage defining bore coaxial to the blind bores for receiving the piston rod.

5. Actuator as in claim 1, including regulator means on one of the heads.

6. Actuator as in claim 1, including valve means on one of the heads.

7. Actuator as in claim 1, the pipe having indexing portions on its two ends respectively fitting in one bore each of each of said heads. 

1. Hydraulic actuator comprising a first cylinder head, a second cylinder head, each provided with plural coaxial, axially staggered blind bores of different diameter and an axial ring face between respective two bores, for receiving pipes of different outer diameter, and for sealingly engaging and positioning such a pipe; a selected pipe having two ends and removably disposed with its two ends in one blind bore each respectively of the first and second heads, a cylindrical wall as defining each bore provided with a groove for receiving a washer, the axial ring face for axial engagement with the respective pipe; means for tightening the two heads towards each other to positively position the pipe between the two heads; and a piston rod with piston disposed in the pipe.
 1. Hydraulic actuator comprising a first cylinder head, a second cylinder head, each provided with plural coaxial, axially staggered blind bores of different diameter and an axial ring face between respective two bores, for receiving pipes of different outer diameter, and for sealingly engaging and positioning such a pipe; a selected pipe having two ends and removably disposed with its two ends in one blind bore each respectively of the first and second heads, a cylindrical wall as defining each bore provided with a groove for receiving a washer, the axial ring face for axial engagement with the respective pipe; means for tightening the two heads towards each other to positively position the pipe between the two heads; and a piston rod with piston disposed in the pipe.
 2. Actuator as in claim 1, the piston removAbly clamped onto the piston rod.
 3. Actuator as in claim 1, the pipe having an axial shoulder near its ends to engage the ring faces of the head.
 4. Actuator as in claim 1, each head including a passage defining bore coaxial to the blind bores for receiving the piston rod.
 5. Actuator as in claim 1, including regulator means on one of the heads.
 6. Actuator as in claim 1, including valve means on one of the heads. 